Field devices, in particular field devices which are used together with sensors to measure fill levels or boundary positions, are often based on delay measurements. In delay measurements, the signal delays of radar signals or guided microwave pulses are determined. The desired measurement value is subsequently determined from these signal delays.
The signals are of a particular frequency and duration. The radar signals and the microwave signals can be allocated to the high-frequency technology (HF technology) range. As signals which are in the high-frequency range, signals in the frequency range up to 2 GHz are generally used as guided microwave signals, and signals in the range of 5 GHz to 79 GHz and above are used as radar signals.
For safety reasons, it may be necessary for the electronics of the field device to be separated from the measurement environment (for example the inside of a container filled with a filling medium) in an explosion-protected manner. The separation consists for example of a gas-tight seal. This can prevent explosive substances or gas mixtures from reaching the electronics of the field device from the container interior and igniting there.
EP 2 093 846 A1 discloses a gas-tight guide feed-through for a field device, which can provide explosion protection of this type. The guide feed-through is coaxial in form and is used for example in a frequency range of between 5 and 28 GHz.